1. If we assume that the duration of life of a leaf in the rice plant was represented by the period from its full emergence to the time when 50 per cent of area of its blade had yellowed, the leaves on a main stem of the plant fertilized completely with nitrogen, phosphorus and potash, in our experiments, lived for periods as follows: the 6 to 8th leaves for 25 days, the 9 to 11th for 30 days and the 12 to 15th for 45 days, each group corresponding to the tilllering, the elongation and the ripening stage of the plant respectively. The last leaf on the main stem lived. for about 50 days. The life duration of leaves of the phosphorus or potash defidient plant in the plots where one of these two elements were omitted, was equal to that of the leaves on the normal plant with complete fertilization. But the time from yellowing of 10 per cent of area of the blade to that of the whole blade was longer in the phosphorus deficiency plot, and snorter in the potash deficiency plot, each compared with that in the complete fertilizer plot. In the no-fertilizer plot, the life of the 7th leaf was shortest, i. e. about 25 days, and the 14th (the last) was longest, i. e. about 52 days, and the time gradient from 8 to 13th leaves were almost constant. Nitrogen deficient leaves in the plot where the nitrogen fertilizer was omitted resembled closely to those in the no-fertilizer plot in their life lengths. 2. Sketches of the yellowing process in the 10th leaf on the main stem of the plant in all the plots were taken on every day. The period from 10-per-cent yellowing to perfect yellowing of the leaf blade on the complete fertilizer plot was 6 days; in the no-potash plot it was 2 days shorter, in the no-phoshorus plot 2 days longer, and both in the no-nitrogen plot and in the no-fertilizer plot they were 4 days longer each compared with that in the complete plot. Notwithstanding remarkable variations in the yellowing process, the tendency above described was found general.
